Mobile communication devices are ubiquitous. Although predominantly cellular telephones, including “smart phones,” the broad classification of mobile communication devices additionally includes Personal Digital Assistants (PDA), portable computers, electronic book readers, and similar electronic devices having communication capabilities, as well as mobile embedded communication devices such as vehicle tracking systems. Many modern mobile communication devices are operative to transmit, receive, store, retrieve, and display/render a broad array of digital content, including text, graphics, images, and audio/video content. Such digital content can be voluminous, and many mobile communication devices are designed to include removable data storage devices, to store and transfer digital content. Additionally, mobile communication devices are often designed with one or more data transfer interfaces. A brief overview of some of these technologies is presented below.
Flash memory is non-volatile, solid state data storage medium. Technically a type of EEPROM, NAND type flash (the most commercially common form of flash memory) is not usually byte-programmable, but must be read, written, and erased on a block basis. Additionally, wear leveling (dynamically remapping the physical memory to evenly spread physical write/erase cycle stress), bad block mapping, and other functions unique to NAND flash memory often require a dedicated memory interface for mass storage devices utilizing NAND flash as a storage medium.
The MultiMedia Card (MMC) is a flash memory card standard that defines the physical dimensions and operational characteristics of a small, removable mass storage device employing NAND flash memory. eMMC embedded memory combines NAND flash memory and a high-speed MMC controller in a standard package. eMMC simplifies system design by freeing a host processor from low-level flash memory management tasks. SD/MMC (Secure Digital) is another standard based on the MMC form factor, which also combines flash memory with an embedded memory controller. The SD controller provides Digital Rights Management (DRM) support. The original SD/MMC cards had a maximum data capacity of 4 GiB. Later developments to the SD standard include SD High Capacity (SDHC), capable of storing up to 32 GiB, and SD Extended Capacity (SDXC), capable of storing up to 2 TiB. SD cards have also been developed in numerous form factors, such as miniSD and microSD. As used herein, the acronym “SD/MMC” encompasses all these and future versions of the Secure Digital MultiMedia Cards. eMMC and SD/MMC card slots are commonly designed into portable consumer electronics, such as digital cameras and mobile phones, as a means of data storage and transfer.
The Universal Serial Bus (USB) is a specification to establish communication between devices and a host controller. Originally designed for personal computers, the USB is intended to replace many varieties of serial and parallel ports. For example, USB connects many computer peripherals such as mice, keyboards, digital cameras, printers, personal media players, flash drives, external hard drives, and the like. Although designed for personal computers, USB has found application in a broad variety of other data communication contexts.
The USB specification has evolved through 3 major revisions. The USB 1.0 specification released in 1996 and updated as USB 1.1 in 1998 introduced Low Speed 1.5 Mbit/s and Full Speed 12 Mbit/s signaling rates. The USB 2.0 specification, released in 2000, added Hi-Speed USB with 480 Mbit/s signaling rate and superseded the USB 1.1 specification. The USB 3.0 specification was released in 2008 and defines an additional SuperSpeed 5 Gbit/s signaling rate using additional wires, separate from the USB 2.0 signaling wires, on an extended SUB connector. To maintain backwards compatibility, SuperSpeed USB controllers and hubs must also include USB 2.0 capabilities and be able to support USB 2.0 and USB 3.0 devices and signaling simultaneously. As used herein, the terms Low Speed, Full Speed, Hi-Speed and SuperSpeed USB have the meaning assigned to them in the USB 2.0 and USB 3.0 specifications, including current and future Engineering Change Notices and addendums, as published by the USB Implementers Forum, Inc. (USB-IF), available at usb.org, and incorporated herein by reference in their entirety.
UniPro (Unified Protocol) is a high-speed interface technology for interconnecting integrated circuits, primarily in mobile phones. UniPro technology provides high-speed data communication (Gbit/s), low-power operation, low pin count, small silicon area, data reliability, and robustness. The theory behind UniPro is the view that the complexity of advanced mobile phones could be reduced by splitting the system design into well-defined functional modules interconnected by a network. Version 1.1 of the UniPro specification was issued in 2009, and is available at http://en.wikipedia.org/wiki/UniPro-cite note-UniPro1.1-2.
Many mobile phones (or more generically herein, mobile platforms) deployed in the field include a USB 2.0 interface, and one or more eMMC or SD/MMC slots. As the USB 3.0 standard is deployed, an increasing number of computers and other devices will be capable of communications at the very high USB 3.0 data rates (5 Gbit/s). Transferring data to and from eMMC and SD/MMC at the high USB 3.0 data rates would be advantageous; however, most existing mobile platforms lack a USB 3.0 interface, and adding one would require extensive redesign and modification.
One proposed solution is to support the data transfer via an external chip, connected to the mobile platform through a UniPro interface, which would access the eMMC or SD/MMC storage memory connected to the external chip, and also transport USB 3.0 traffic. However, this requires a UniPro interface at the platform level. Integration of such an external chip in the mobile platform is complex, and would require extensive software modification. Since all access to the eMMC or SD/MMC cards by the mobile platform would be performed through the UniPro interface, the external chip would have to be fully operational at all times. This would increase power consumption and reduce the lifespan of the mobile platform between battery charges or changes.